1. Field of the Invention
The present invention relates to an active roll control system. More particularly, the present invention relates to an active roll control system (ARCS) that actively controls roll of a vehicle by changing torsional rigidity of a stabilizer bar by using change in tension of a wire according to an operation of a pulley unit mounted at an lower arm, simplifies control of the ACRS as a consequence that an electric motor controls operation of the pulley unit, and has advantages in layout.
2. Description of Related Art
Generally, a suspension system of a vehicle connects an axle to a vehicle body so as to control vibration or impact transmitted from a road to the axle when driving not to be directly transmitted to the vehicle body. Accordingly, the suspension system of a vehicle prevents the vehicle body and freight from being damaged and improves ride comfort.
Such a suspension system, as shown in FIG. 1, includes a chassis spring 101 relieving impact from the road, a shock absorber 103 reducing free vibration of the chassis spring 101 and improving the ride comfort, and a stabilizer bar 105 suppressing roll of a vehicle (it means that a vehicle inclines with reference to a length direction of the vehicle body).
Both sides of the stabilizer bar 105 is mounted at the vehicle body 107, and both ends of the stabilizer bar 105 is mounted at a lower arm 109 or a strut bar (not shown). Therefore, in a case that left and right wheels 111 move to the same direction (upward direction or downward direction), the stabilizer bar 105 does not work. On the contrary, in a case that the left and right wheels 111 move to the opposite direction (one moves upwardly and the other moves downwardly), the stabilizer bar 105 is twisted and suppresses the roll of the vehicle body 107 by torsional restoring force.
That is, when the vehicle body 107 inclines toward a turning axis by the centrifugal force in a case of turning or heights of the left and right wheels is different from each other by bump or rebound of the vehicle, the stabilizer bar 105 is twisted and stabilizes position of the vehicle body by torsional restoring force.
However, a conventional stabilizer bar 105 suppresses inclination of the vehicle or restores the inclined vehicle body 107 by only using torsional restoring force of the stabilizer bar 105, it is difficult to control roll of the vehicle quickly and precisely. In order to solve above-mentioned problem, an active roll control system provided with an actuator having a hydraulic pressure cylinder 113 connected to one end of stabilizer bar 105 and controlling the roll of the vehicle actively is developed.
According to an active roll control system that controls the roll of the vehicle actively by using the hydraulic pressure cylinder 113, one lower arm 109 is connected to one end of the stabilizer bar 105 by a stabilizer link 115 and the other lower arm 109 is connected to the other end of the stabilizer bar 105 by the hydraulic pressure cylinder 113, as shown in FIG. 2. Therefore, the active roll control system stabilizer bar 105 changes torsional rigidity of the stabilizer bar 105 by changing a length between the other end of the stabilizer bar 105 and the lower arm 109.
That is, according to the active roll control system, a lower end of the hydraulic pressure cylinder 113 is connected the other lower arm 109, and an upper end of piston rod 117 of the hydraulic pressure cylinder 113 is connected to the other end of the stabilizer bar 105 by a ball joint 119.
Therefore, an ECU controls a hydraulic pressure system including a valve and a hydraulic pressure pump based on signals output from an acceleration sensor, a vehicle height sensor, and a steering sensor, and improves the roll of the vehicle according to the active roll control system.
However, according to the conventional active roll control system, a lower end of the hydraulic pressure cylinder 113 (i.e., actuator) must be assembled to the lower arm 109 through an additional bracket 121 in order to guarantee an operational stroke thereof. However, such structures have drawbacks in mass productivity.
In addition, the hydraulic pressure supply system for supplying and controlling hydraulic pressure including a hydraulic pressure pump, a hydraulic pressure valve, and a hydraulic line is very complex according to the conventional active roll control system.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.